Exhaust-gas turbocharger

ABSTRACT

An exhaust-gas turbocharger ( 1 ) having a shaft ( 2 ), which has a first centric bore ( 4 ) on an end face ( 3 ), a turbine wheel ( 5 ), which has a second centric bore ( 7 ) in the wheel rear side ( 6 ) thereof, a connection piece ( 8 ), which engages into the first and second bores ( 4, 7 ); and an integral connection device ( 9 ) for connecting the shaft ( 2 ) to the turbine wheel ( 5 ), wherein the connection piece ( 8 ) is hollow in form.

The invention relates to an exhaust-gas turbocharger according to the preamble of claim 1.

An exhaust-gas turbocharger of this type is known from DE 10 2009 034 420 A1. To connect the turbine wheel of this known exhaust-gas turbocharger to a steel shaft, it is provided to make a bore both in the wheel rear side of the turbine wheel and in the end face of the shaft, into which bore there is inserted a metallic centering pin, the coefficient of thermal expansion of which corresponds substantially to that of the ceramic turbine wheel. Furthermore, a soldered connection is provided to connect the shaft and the turbine wheel.

The disadvantage of this arrangement is that the centering pin forms a heat bridge, and therefore a high quantity of heat is introduced from the turbine wheel into the shaft.

It is an object of the present invention, therefore, to provide an exhaust-gas turbocharger of the type indicated in the preamble of claim 1 which makes it possible to realize a heat throttle between the turbine wheel and the shaft.

This object is achieved by the features of claim 1.

According to the invention, it is provided that the connection piece inserted into the bores in the turbine wheel and the shaft is hollow in form. Accordingly, an air space which acts as a heat throttle is formed in the connection piece. The connection piece can in this respect be in the form of a bored-out sleeve or of a clamping sleeve.

The connection piece thus performs the task of a heat throttle as well as the task of a centering part between the turbine wheel and the shaft.

The dependent claims relate to advantageous developments of the invention.

In particular, the connection piece can be in the form of a circular-cylindrical part or of a part with an angular cross section. In the latter case, in addition to the integral connection, there is also a form fit between the turbine wheel and the shaft.

In principle, soldered connections, adhesively bonded connections or else welded connections are conceivable as integral connections.

Claims 9 and 10 define a rotor according to the invention of an exhaust-gas turbocharger as an object which can be marketed independently.

Further details, advantages and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the drawing, in which:

FIG. 1 shows a schematically greatly simplified basic illustration of an exhaust-gas turbocharger according to the invention, and

FIG. 2 shows a partial section through the shaft and the turbine wheel of a rotor of the exhaust-gas turbocharger according to the invention in the region of the point of attachment between the turbine wheel and the shaft.

FIG. 1 shows, in a schematically greatly simplified illustration, an exhaust-gas turbocharger 1 having a shaft 2. A turbine wheel of a turbine 4 is arranged at one end of the shaft 2. The other end of the shaft 2 is provided with a compressor wheel 10 of a compressor 11. A bearing housing 12 for mounting the shaft 2 is provided between the compressor 11 and the turbine 4. The exhaust-gas turbocharger according to the invention of course also has all the further parts of such chargers, but these are not shown or explained since they are not required for explaining the principles of the present invention.

As FIG. 2, in particular, shows, the shaft 2 has a first centric bore 4 on an end face 3 facing toward the turbine wheel 5.

The turbine wheel 5 has a second centric bore 7 in the wheel rear side 6 thereof. These bores 4 and 7 are arranged in alignment with the longitudinal axis L of the exhaust-gas turbocharger 1. In the embodiment shown, the wheel rear side 6 of the turbine wheel 5 is in the form of a shoulder protruding axially in the direction toward the shaft 2. It is also possible, however, for the wheel rear side 6 to be formed with a smooth surface.

As FIG. 2 shows, provision is made of a connection piece 8, which, in the assembled state shown in FIG. 2, engages into the first and the second bores 4 and 7. To connect the turbine wheel 5 and the shaft 2, provision is furthermore made of an integral connection device 9, which, as mentioned in the introduction, can be in the form of a soldered connection, for example.

FIG. 2 shows that the connection piece 8 is in the form of a hollow sleeve having an inner space 13 which accommodates an air cushion as a heat throttle. The connection piece 8 thus serves both as a centering piece and as a heat throttle, which reduces the introduction of heat from the turbine wheel 5 into the shaft 2. In this respect, it is of course possible to adapt the length and diameter of the connection piece 8 to the respective application, in order to achieve the highest possible heat throttle action. Furthermore, it is in principle likewise conceivable to extend the bores 4 and 7 beyond the length of the connection piece 8, in order to lengthen the air space 13 beyond the connection piece 8.

Accordingly, the connection piece 8 can be in the form of a bored-out sleeve or of a hollow clamping sleeve.

It may have a circular-cylindrical cross section or else an angular cross section in order to achieve a form-fitting connection in addition to the integral connection.

The turbine wheel is preferably formed from titanium aluminide (TiAl). The shaft 2 is preferably in the form of a steel shaft.

In addition to the above written disclosure of the invention, reference is hereby explicitly made to FIGS. 1 and 2 to supplement the disclosure.

LIST OF REFERENCE SIGNS

-   1 Exhaust-gas turbocharger -   2 Shaft -   3 End face -   4 First centric bore -   5 Turbine wheel -   6 Wheel rear side -   7 Second centric bore -   8 Connection piece -   9 Integral connection device -   10 Compressor wheel -   11 Compressor -   12 Bearing housing -   L Charger longitudinal axis 

1. An exhaust-gas turbocharger (1) having a shaft (2), which has a first centric bore (4) on an end face (3); a turbine wheel (5) having a wheel rear side (6), which has a second centric bore (7) in the wheel rear side (6) thereof; a connection piece (8), which engages into the first and second bores (4, 7); and an integral connection device (9) for connecting the shaft (2) to the turbine wheel (5), wherein the connection piece (8) is hollow in form.
 2. The exhaust-gas turbocharger as claimed in claim 1, wherein the connection piece (8) is in the form of a bored-out sleeve.
 3. The exhaust-gas turbocharger as claimed in claim 1, wherein the connection piece (8) is in the form of a hollow clamping sleeve.
 4. The exhaust-gas turbocharger as claimed in claim 1, wherein the connection piece (8) has a circular-cylindrical cross section.
 5. The exhaust-gas turbocharger as claimed in claim 1, wherein the connection piece (8) has an angular cross section.
 6. The exhaust-gas turbocharger as claimed in claim 1, wherein the turbine wheel (5) is formed from TiAl material.
 7. The exhaust-gas turbocharger as claimed in claim 1, wherein the shaft (2) is formed from steel.
 8. The exhaust-gas turbocharger as claimed in claim 1, wherein the integral connection device (9) is a soldered, adhesively bonded or welded connection.
 9. A rotor of an exhaust-gas turbocharger (1), having a shaft (2), which has a first centric bore (4) on an end face (3); a turbine wheel (5) having a wheel rear side (6), which has a second centric bore (7) in the wheel rear side (6) thereof; a connection piece (8), which engages into the first and second bores (4, 7); and an integral connection device (9) for connecting the shaft (2) to the turbine wheel (5), wherein the connection piece (8) is hollow in form.
 10. The rotor as claimed in claim 9, wherein the connection piece (8) is in the form of a bored-out sleeve.
 11. The rotor as claimed in claim 9, wherein the connection piece (8) is in the form of a hollow clamping sleeve.
 12. The rotor as claimed in claim 9, wherein the connection piece (8) has a circular-cylindrical cross section.
 13. The rotor as claimed in claim 9, wherein the connection piece (8) has an angular cross section.
 14. The rotor as claimed in claim 9, wherein the turbine wheel (5) is formed from TiAl material.
 15. The rotor as claimed in claim 9, wherein the shaft (2) is formed from steel.
 16. The rotor as claimed in claim 9, wherein the integral connection device (9) is a soldered, adhesively bonded or welded connection. 